• 대한원격탐사학회지
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• 제33권1호
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• pp.47-60
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• 2017

The permafrost active layer plays an important role in permafrost dynamics. Ecological patterns, processes, and water and ice contents in the active layer are spatially and temporally complex depending on landscape heterogeneity and local-scale variations in hydrological processes. Although there has been emerging interest in the application of optical remote sensing techniques to permafrost environments, optical sensors are significantly limited in accessing information on near surface geo-cryological conditions. The primary objective of this study was to investigate capability of L-band SAR data for monitoring spatio-temporal variability of permafrost ecosystems and underlying soil conditions. This study exploits information from different polarimetric SAR observables in relation to permafrost environmental conditions. Experimental results show that each polarimetric radar observable conveys different information on permafrost environments. In the case of the dual-pol mode, the radar observables consist of two backscattering powers and one correlation coefficient between polarimetric channels. Among them, the dual-pol scattering powers are highly sensitive to freeze/thaw transition and can discriminate grasslands or ponds in thermokarst area from other permafrost ecosystems. However, it is difficult to identify the ground conditions with dual-pol observables. Additional backscattering powers and correlation coefficients obtained from quad-pol mode help understanding seasonal variations ofradar scattering and assessing geo-cryological information on soil layers. In particular, co-pol coherences atHV-basis and circular-basis were found to be very usefultools for mapping and monitoring near surface soil properties.

• 한국군사과학기술학회지
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• 제21권2호
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• pp.166-172
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• 2018

To develop and evaluate the real-time SAR(Synthetic Aperture Radar) motion measurement system, true antenna phase center(APC) positions during SAT(Synthetic Aperture Time) are needed. In this paper, CDGPS(Carrier phase Differential Global Positioning System) post processing method is proposed to get the true APC position for spotlight SAR image formation. The CDGPS position is smoothed to remove high frequency noise which exists inherently in the carrier phase measurement. This paper shows smoothed CDGPS data is enough to provide the true APC for high-quality SAR image formation through motion measurement result, phase error estimation and IRF(Impulse Response Function) analysis.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2006년도 추계학술발표회
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• pp.193-199
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• 2006

본 논문은 열대저기압, 태풍 및 허리케인의 연구와 분석에 사용되는 몇 가지 마이크로파 방식들을 검토하였다. 마이크로파 신호는 폭풍 속 구름과 비에 의해 잘 흡수되지 않는 장점을 가지기 때문에 격렬한 폭풍을 동반하는 열대저기압의 관측에 있어 매우 유용하다. 그에 대한 장비들로 산란계(scsatterometers), 마이크로파 복사계(microwave radiometers), 합성개구레이더 (synthetic aperture radars; SARs), 강우레이더 (rain radar) 에 대해 살펴보았다. 이러한 마이크로파 장비들로부터 얻어진 열대저기압내의 바람, 강우, 구름분포와 같은 자료들은 태풍의 진로와 강도예측에 중요한 정보를 제공한다. ERS-1, 2 산란계와 RADARSAT-1 SAR로부터 얻어진 세부적인 바람장, 넓은 관측범위를 가지는 SSM/I 로부터 얻은 풍속분포, 높은 해상도를 가지는 TRMM 강우레이더의 강우 강도측정들은 이러한 예를 보여주고 있다. 초기 마이크로파 원격탐사에서 나타났던 해상도, 관측 폭과 같은 한계들은 최근 발사되어 운영되는 위성들의 장비들로 많은 개선이 이루어졌다. 이러한 마이크로파 장비들에 대한 충분한 이해와 활용은 열대저기압의 발생과 강도와 같은 특성들을 규명하는데 큰 역할을 할 것이다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.574-576
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• 2004

Since variance of noise is important parameter for a noise filter to reduce noise in image and the performance of noise filter is dependent on estimated variance. In this paper, we apply additive noise variance estimation method to estimate variance of speckle noise of synthetic aperture radar (SAR) imagery. Generally, speckle noise is in multiplicative model, logarithmic transformation is then used to transform multiplicative model into additive model. Here, speckle noise is generally modeled as Gamma distribution function with different looks. The additive noise variance estimation is processed in log domain. The synthesis image and real image of SAR are implemented to test and confirm results and show that more accurate estimation can be achieved.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.445-448
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• 2007

Korea Peninsula is exposed to landslide problems because large regions of Korea are composed of mountain. As a result, we have a great loss of life and property every year, such as road, bridge, and building. However, conventional survey has many restrictions of time and man power. In recent days, instead of field surveying, remote sensing has our attention for detecting damaged place. Synthetic Aperture Radar (SAR) provides the all-weather capability and complements information available. And through the 2-pass DInSAR technique, we can measure even very small displacement effect. In this study, we generated six interferograms of Kangwondo between 1992 and 1998, and estimated the vulnerable place for landslide.

• 한국태양에너지학회 논문집
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• 제37권5호
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• pp.49-63
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• 2017

Solar cells have widely been utilized for a satellite to convert sunlight energy into electricity in space. Many different types of solar cells appropriate for each satellite program are available in current markets, which enables us to construct a solar array light and small often required from a low Earth orbit (LEO) synthetic aperture radar (SAR) satellite. Thus, it is important to choose a proper solar cell satisfying the requirements of mass and size for the solar array. In this article, we have surveyed typical suppliers and have discussed some characteristics of solar cells. Conceptual design examples of the solar array for LEO SAR satellites using several types of solar cells have been performed to show the pros and cons of solar cells by comparison of the total mass and size necessary for the solar array.

• 대한원격탐사학회지
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• 제10권2호
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• pp.161-170
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• 1994

The JERS-1 is an Earth Resources Satellite launched by NASDA (Natinal Space Development Agency) of Japan, in February in 1992 and has two sensors; SAR(L-Band Synthetic Aperture Radar) and OPS (SWIR and VNIR radiometers). In this research note, the basic properties and data characteristics of the SAR data are summarized based on the observations made on the data sets received for the Nahanni Canadian test site, Northwest Territories. The JERS-1 SAR data quality. including the spatial resolution of the data, is, in general, excellent for most geological applications.

• 대한원격탐사학회지
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• 제38권4호
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• pp.375-386
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• 2022

The city of Khartoum, the capital of Sudan, was heavily damaged by the flood of the Nile in 2020. Classification using satellite images can define the damaged area and help emergency response. As Synthetic Aperture Radar (SAR) uses microwave that can penetrate cloud, it is suitable to use in the flood study. In this study, Random Forest classifier, one of the supervised classification algorithms, was applied to the flood event in Khartoum with various sizes of the training dataset and number of images using Sentinel-1 SAR. To create a training dataset, we used unsupervised classification and visual inspection. Firstly, Random Forest was performed by reducing the size of each class of the training dataset, but no notable difference was found. Next, we performed Random Forest with various number of images. Accuracy became better as the number of images in creased, but converged to a maximum value when the dataset covers the duration from flood to the completion of drainage.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.530-533
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• 2005

A raw signal simulator for synthetic aperture radar (SAR) is a useful tool for the design and implementation of SAR system. Also, in order to analyze and verify the developed SAR processor, the raw signal simulator is required. Moreover, there is the need for a test system to help designing new SAR sensors and mission of SAR system. The derived parameters of the SAR simulator also help to generate accurate SAR processing algorithms. Although the ultimate purpose of this research is to presents a general purpose SAR simulator, this paper presents a SAR simulator in frequency domain at the first step. The proposed simulator generates the raw signal by changing various simulation parameters such as antenna parameters, modulation parameters, and sampling parameters. It also uses the statistics from an actual SAR image to imitate actual physical scattering. This paper introduces the procedures and parameters of the simulator, and presents the simulation results. Experiments have been conducted by comparing the simulated raw data with original raw SAR image. In addition, the simulated raw data have been verified through commercial SAR processing software.

• 한국위성정보통신학회논문지
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• 제1권1호
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• pp.26-39
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• 2006

영상 레이다(SAR)는 전천후 영상획득이 가능하며, 반사표면의 물리적인 구조와 특성에 따라 표적탐지 및 식별성능이 우수하므로 군사용으로는 물론 과학 민수용으로 광범위한 활용분야를 가지고 있다. 본 논문에서는 먼저 X-밴드 소형위성 SAR 체계 설계 개념과 주요 임무 및 체계설계 요건들을 제시하고 이를 만족시키기 위한 영상모드 설계 기법과 표준 영상모드 설계 결과를 분석한다. 그리고, X-밴드 SAR 탑재체 및 지상 수신처리의 주요 체계 설계 결과와 성능특징을 제시하고, 마지막으로 SAR 영상활용을 위한 응용분야와 처리결과를 제시한다. 제안된 위성 SAR 시스템은 광역감시 모드에서 고해상도 모드까지 다양한 영상 모드 구현이 가능하며, 소형, 고성능, 저 비용 관점에서 효율적인 전천후 레이다 영상획득 시스템이다.